Recently, so-called electronic pet devices (or breeding simulation game machines) have been popular because of the easiness in comparison with breeding of real animals as pets.
In an electronic pet device, an object of a virtual living body is displayed as an electronic pet and a keeper (user of the electronic pet device) is notified of the state of the electronic pet such as the degree of starvation (hunger) or fatigue by an image or a sound. The keeper (user) feeds or plays with the electronic pet by operating the electronic pet device in accordance with the state of the electronic pet. Thus, the electronic pet has its state (state of the electronic pet) changed on the basis of the keeper's actions and is thus bred. The electronic pet grows with the lapse of time and therefore the state of the electronic pet is also changed with the lapse of time.
Meanwhile, since the electronic pet device only displays the electronic pet on the display screen, the displayed electronic pet is a so-called virtual existence.
In the case where the electronic pet is realized by means of, for example, a robot, which exists as a substance, the robot as the electronic pet actually exists in the real world. In such a case, with respect to the robot as the electronic pet, the keeper (user) will have a feeling closer to the feeling in the case of actually breeding a pet, than with the electronic pet displayed in the electronic pet device.
However, in the case where the electronic pet is realized by means of a robot, it is inconvenient to carry the robot in traveling or the like. Therefore, it is more convenient if the electronic pet can be realized as an actually existing robot in a certain case and can be realized as a virtual existence in a portable electronic pet device in another case.
Since the electronic pet realized in the conventional electronic pet device generally has its state changed in accordance with an input from the user or with the lapse of time and thus takes an action, it lacks reality in comparison with the case of breeding a real animal as a pet.
Specifically, for example, in the case where a dog as a real animal is bred as a pet, when the dog wants the keeper to play with him, the dog barks or wags his tail to draw the keeper's attention. In this case, if the keeper keeps ignoring, the dog gets tired and stops barking or wagging his tail and then takes an action such as falling asleep. The real pet animal may be in high spirits after sleeping.
On the other hand, the electronic pet realized in the conventional electronic pet device (for example, an electronic pet dog) continues barking or wagging its tail when wanting the keeper to play, or stops such an action due to the lapse of time. Unlike the real pet animal (for example, a dog), the electronic pet does not get tired and fall asleep through barking or wagging its tail. That is, in the electronic pet realized in the conventional electronic pet device, the state of the electronic pet is not changed in accordance with the action of the electronic pet itself, and therefore does not take any action in accordance with such a change of the state due to the action of the electronic pet itself. For these reasons, it is demanded to provide an electronic pet with more reality.